• First cells originated in water, where oceans shielded early life from UV radiation
• Water remains the medium for most life processes and forms much of cell mass
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Start with the concept explanation, then practise to create mastery evidence.
2
Learning objective
A1.1.2—Hydrogen bonds in water
New
• O-H covalent bonds and water's V-shape make molecules polar
• Hydrogen bonds form between water molecules, not within a molecule
• Hydrogen bonding explains many unusual water properties
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Start with the concept explanation, then practise to create mastery evidence.
3
Learning objective
A1.1.3—Cohesion of water molecules
New
• Hydrogen bonding creates cohesion and surface tension
• Cohesion prevents xylem water columns breaking under tension
• Surface tension supports droplets and surface-skating insects
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Start with the concept explanation, then practise to create mastery evidence.
4
Learning objective
A1.1.4—Adhesion of water
New
• Water adheres to polar or charged surfaces
• Adhesion supports capillary action in soil channels and cellulose cell walls
• Cohesion is the stronger force in xylem transport; adhesion helps refill vessels
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Mistakes
Start with the concept explanation, then practise to create mastery evidence.
5
Learning objective
A1.1.5—Solvent properties of water
New
• Water dissolves ions and polar molecules by hydration and hydrogen bonding
• Aqueous solution enables diffusion, transport, enzyme activity, and metabolism
• Non-polar molecules are hydrophobic; O₂ and N₂ have low solubility in water
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Start with the concept explanation, then practise to create mastery evidence.
6
Learning objective
A1.1.6—Physical properties of water for aquatic animals
New
• Specific heat capacity stabilizes aquatic temperatures and body temperature
• Thermal conductivity, buoyancy, and viscosity shape aquatic adaptations
• Compare black-throated loon and ringed seal adaptations for diving, insulation, and movement
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Mistakes
Start with the concept explanation, then practise to create mastery evidence.